Sulfur slurry preparation in pipelines

ABSTRACT

AN IMPROVED SULFUR-PETROLEUM OIL FRACTION SLURRY RESISTANT TO AGGLOMERATION BY ADDITION THERETO OF A SMALL AMOUNT OF CRUDE OIL.

US. Cl. 252309 4 Claims ABSTRACT OF TIE DISCLOSURE atent An improved sulfur-petroleum oil fraction slurry resistant to agglomeration by addition thereto of a small amount of crude oil.

CROSS-REFERENCE This application is a division of co-pending application Ser. No. 784,924, now US. Pat. No. 3,582,146.

BACKGROUND OF THE INVENTION The transportation of sulfur neat or as a water or oil slurry in pipelines is well known in the art as noted by reference to US. Pats 2,798,772; 2,917,345 or 2,947,578 or as described in Pipeline Industry, June 1967, pp. 58- 60. In making the sulfur into a sulfur-hydrocarbon slurry, the sulfur is generally sprayed in molten form into either water or a hydrocarbon to form a slurry suitable for transportation through a pipeline. Formation of a stable slurry wherein the sulfur does not undergo any undesirable change or the slurry does not exhibit a tendency to wide variation in viscosity is essential to the process in addition to other problems which may be encountered during and after transportation of the slurry through a pipeline. Thus, agglomeration and separation of the sulfur from the carrier fluid, plating, depositing or coating of the sulfur on pipeline walls causing plugging of the pipeline, corrosion, viscosity changes due to pressure and temperature variations requiring greater pumping power which increases operation costs, etc., are only a few of the problems normally encountered in transporting sulfurliquid hydrocarbon slurries through pipelines.

Although the above are serious problems for consideration in transporting sulfur through pipelines, nevertheless the transportation of sulfur in slurry form through pipelines can be made to be an effective, attractive and economic means of sulfur transportation, particularly since sulfur is recovered or obtained from isolated, remote and inaccessible areas, and must be transported to desired accessible areas. As noted above, a number of methods have been proposed for pipeline transportation of sulfur slurries such as injecting molten sulfur into water or a liquid hydrocarbon thereby forming a sulfur slurry for pipeline transportation. These methods for making sulfur slurries suitable for transporting through pipelines generally do not overcome the agglomeration, deposition, sticking, coating and/or plugging problems described above.

An object of the present invention is to transport sulfur as a sulfur-liquid hydrocarbon slurry through pipelines which is stable and flowable.

Still another object of the present invention is to transport through a pipeline sulfur-liquid hydrocarbon slurries without causing sulfur agglomeration, coating, deposition or plugging of the pipeline.

Still another object of this invention is to form a slurry of sulfur in a liquid hydrocarbon medium, which does not 3,745,121 Patented July 10, 1973 tend to cause sticking, agglomeration or pipeline plugging or cause any difliculty in circulation of the slurry when said slurry is pumped and transported through a pipeline and from which the sulfur can be readily recovered at the terminal end of the pipeline as essentially pure sulfur.

Another object is to transport sulfur as a liquid hydrocarbon slurry by pipeline over great distances under conditions of reduced pumping and handling costs.

Other objects will be apparent from the following description.

SUMMARY OF THE INVENTION The present invention is directed to an improved, novel and new technique for transporting a slurry of a sulfurliquid petroleum fraction through pipelines over great distances without causing sulfur agglomerations or sticking or sulfur deposition on the walls of the pipelines due to the tendency of sulfur under such conditions to adhere to the pipeline walls because of temperature, pressure and other variable conditions so as to plug said lines; by admixing or adding or injecting prior to or after injection into the pipeline of a slurry of sulfur and a liquid petroleum fraction, which fraction can be a distillate or condensate petroleum fraction ranging in viscosity from a gasoline to a heavy lube oil fraction such as gasoline, kerosene, fuel oil, lubricating oil and fractions and mixtures thereof, a small amount of from 0.1% to 10%, preferably between about 0.5% to about 5%, of a crude oil which can be refined or unrefined and preferably an unrefined crude oil. The crude oil can be added to the slurry or sulfur and liquid petroleum fraction as described prior to or during the making of the slurry or the crude oil can be injected when necessary in various places along the pipeline where indications are that the slurry might cause sulfur agglomeration, deposition, sticking or plugging of the line. Any plugging detection means known in the art can be used for this purpose. It has been noted that by adding or injecting into a slurry of the sulfur and liquid petroleum fraction, e.g., kerosene or oil condensate, before, during or after the slurry preparation, from about 0.1 to 10% of crude oil in which the sulfur content of the slurry can vary from about 10% to about by weight or higher, preferably between 30 and 70% by weight sulfur, that not only does the presence of the crude oil prevent plugging of pipelines transporting said slurry but also preventing agglomeration, sticking and deposition of sulfur on the walls of the pipelines and improves flow of the slurry and reduces pumping costs.

The sulfur-liquid petroleum fraction slurry can be made by any suitable means such as described in US. Pat. 2,798,772 or by the method described in US. Pat. 3,443,- 837. It is preferred that in the making the sulfur-liquid petroleum fraction slurry that the sulfur is produced in spherical form since sulfur in this form in the slurry is resistant to agglomeration, attriction and friction.

The phase transfer method for making the sulfur slurry as described in the above-mentioned copending application comprises first forming a sulfur-aqueous liquid (water) slurry and thereafter phase transferring the sulfur particles from the aqueous liquid into a liquid hydrocarbon. The sulfur may be phase transferred directly into crude oil. Thereafter, the crude oil can be added as desired.

The liquid petroleum carrier for the sulfur can be one ranging in viscosity from a light petroleum fraction such as liquefied petroleum gas (LPG), gasoline, kerosene, fuel oil, lube oil, petroleum distillates, condensates, and mixtures thereof. Preferred are liquid petroleum fractions containing at least 10% or higher of aromatics, preferably about 15-30% aromatic enriched kerosene or oil condensate fractions containing 15-20% aromatics which include monoand polyaromatic hydrocarbons. The carrier may be 100% crude oil.

The crude oil additive should be unrefined crude oil. By unrefined crude oil is meant any crude oil which has not been processed in a refinery. Thus, a crude oil may be used as it is removed from the ground, or it may be first processed in field units such as oil-water separators, degasers, etc. Although just how the crude oil functions in this manner in the slurry mixture is not understood, it is believed that the crude oil contains surface-active components or agents which prevent sulfur agglomeration, sticking and aids in the formation of spherical sulfur particles having dimensions of from 1 to 1500 microns and preferably between 100 and 700 microns.

At the terminal end of the line the sulfur can be readily separated from the slurry by any suitable means.

PREFERRED EMBODIMENT OF THE INVENTION (I) A 40-60% by weight sulfur-aromatic (17%) en- 4 by volume in which the sulfur particles Were essentially large angular-crystalline particles which began to stick together and agglomerate into a sticky mass within about 10-15 minutes.

(B) The method of (A) was repeated except that 1% of crude oil was added to the kerosene carrier. The particles formed were microspherical (-450 microns) in shape and no tendency of the particles to stick or agglomerate was observed for over 24 hours.

In another test different petroleum fractions were used to form sulfur slurries wherein a 90-ml. portion of molten sulfur at 140 C. was injected as a continuous stream for 0.5 minute into a Well-stirred 500 ml. charge of a petroleum carrier. As shown in Table 1 some of the carriers were used neat and to some were added crude oil For com; parison various surfactants were added to sulfur-oil slurries and the results are shown in Table 1.

TABLE 1.-EFFE C'I OF ADDITIVES ON SULFUR DISPERSION [Conditions: 500 ml. carrier in l-liter Morton flask. 90 ml. sulfur at approximately 140 C. added in 0.6 minute. 1,200 r.p.m. with crescent blade stirrer] Coagulum Major fractions, per- (+12 mesh) cent weight basis Initial Level, percent slurry temp., percent w ight Particle Run Carrier 0. weight Type basis S fed -16, 30, +50 1150, Shape 1 Pztroleun fracttion (Water- 22 None 19.1 57.7 19.3 680 A on con ensa e 2 do. -3 22 1 Bryton 430 (62% alkylaryl 20.4 60.0 21.0 710 A sulfonate). 24 1 Oleic acid 23 1 Naphthenic acid bottoms 23 1 Dehydroabietic acid. 21 1 50% dodecyltrimethylammonium chloride. 7 kerosene/white oil 23 0 1 6 API crude oil (Waterton condensate).

hEl=spherical, A=agglomerated, in estimated order of abundance in +30 mesh fraction.

600 r.p.m. in early scouting runs and in all 60 0. runs.

Derived from Canadian oil field. API gravity=54.9; viscosity, cs. 59 F.=0.953 and 77 E.=0.865; flash point, tag open cup, F.=7; pour point, F.= 80; sulfur, percent weight t0tal=1.14; FIA, percent volume saturates=82 and aromat1cs=18.

riched kerosene slurry was prepared by phase transfer by first injecting molten sulfur into an aqueous liquid such as water and thereafter contacting the slurry thus formed with the aromatic enriched kerosene to effect phase transfer of the sulfur particles into the aromatic enriched kerosene. To the sulfur-kerosene slurry was added from about 1% to about 2% of crude oil and thereafter this slurry was injected into a pipeline for transporation to a terminal station. Sulfur-kerosene slurries containing a small amount of crude oil thus formed do not form agglomerates nor did they plug the pipeline.

(II) An advantage of the present process for transporting through pipelines sulfur-liquid petroleum slurries as defined is that the slurry can be also prepared by direct injection of molten sulfur into a suitable petroleum fraction such as kerosene, fuel oil, oil condensate or distillate and mixtures thereof to which has been added a small amount of crude oil so as to aid in making spherical sulfur particles and prevent sulfur agglomeration, deposition and plugging of pipelines. Either process as well as other processes can be used to make the sulfur-liquid petroleum fraction slurry depending on the availability of the carrier. Thus, where water is available the first process can be used and if not the second one can be used.

The presence of a small amount of crude oil during the preparation of the final slurry by method (I) or (II) has an additional advantage in that the crude oil aids in the formation of spherical sulfur particles which are most desirable since spherical sulfur particles in slurries as defined provide optimum pipeline performance such as low pressure drops during its transportation and ease of recovery and purification at the terminal end of the pipeline.

The following examples illustrate 'the essence of the present invention.

(A) Molten sulfur at 120-160 C. was sprayed into aromatic (17%) enriched kerosene through a spray nozzle at about 200 p.s.i. pressure drop to give a homogeneous slurry with sulfur solids content of about 16% Sulfur slurries of the present invention containing small amounts of crude oil additives can be transported through pipelines over great distances without the danger of sulfur deposition, agglomeration, sticking or plugging of the pipelines.

At the terminal end of the line the sulfur can be removed from the liquid hydrocarbon by suitable means such as described in US. Pat. 2,798,772 and the sulfur purified by methods as described in Us. Pat. 2,809,885 or as described in US. Pat. 3,489,677 which comprises treating oil contaminated sulfur with an aqueous solution containing a mixture of alkali hydrosulfide and corresponding hydroxide, e.g., ammonium hydrosulfide and ammonium hydroxide, or by other suitable means such as sulfur can be recovered from the oil slurry by filtration of molten sulfur and liquid-liquid extraction with a hydrocarbon solvent containing 1050% aromatic. Thus, at the receiving terminal the sulfur slurry can be filtered and washed. The recovered sulfur is then melted and purified by liquid-liquid extraction with an aromatic hydrocarbon such as cumene. Also, if desired, the filtered sulfur can be steam stripped to recover bright yellow sulfur.

The foregoing description of the invention is merely intended to be explanatory thereof. Various changes in the details of the described method may be made within the scope of the appended claims without departing from the spirit of the invention.

We claim as our invention:

1. A stable non-agglomerating sulfur-liquid petroleum slurry comprising 1075% sulfur in a liquid petroleum fraction selected from the group consisting of distillate petroleum fractions and condensate petroleum fractions and ranging in viscosity from gasoline to a heavy lube oil and including from about 0.1% to about 10% crude oil.

2. The slurry composition of claim 1 wherein the petroleum fraction is a petroleum condensate containing from 10% to 30% aromatics and the crude oil is present in amounts from 0.5% to 5%.

5 6 3. The slurry composition of claim 1 wherein the References Cited petroleum fraction is a petroleum distillate containing UNITED STATES PATENTS from 10% to 30% aromatics and the crude oil is present in amounts from 0.5% to 5%.

4. A stable non-agglomerating sulfur-liquid petroleum slurry comprising 10-75% slurry in a liquid petroleum 3,476,441 11/1969 Elliott 302- 66 5 JOHN D. WELSH, Primary Examiner fraction selected from the group consisting of gasoline, Us Cl XR kerosene, fuel oil, and lubricating oil and including from 3O2 66 about 0.1% to about 10% of oil more viscous than said liquid petroleum fraction and selected from the group 10 consisting of refined crude oil and unrefined crude oil. 

